scholarly journals Accretion, retreat and transgression of coastal wetlands experiencing sea-level rise

2021 ◽  
Vol 25 (2) ◽  
pp. 769-786
Author(s):  
Angelo Breda ◽  
Patricia M. Saco ◽  
Steven G. Sandi ◽  
Neil Saintilan ◽  
Gerardo Riccardi ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Wetlands ◽  
Coastal Wetland ◽  
Sediment Load ◽  
Tidal Range ◽  
Sediment Distribution ◽  
Eastern Australia ◽  
And Migration ◽  
Inner Channel

Abstract. The vulnerability of coastal wetlands to future sea-level rise (SLR) has been extensively studied in recent years, and models of coastal wetland evolution have been developed to assess and quantify the expected impacts. Coastal wetlands respond to SLR by vertical accretion and landward migration. Wetlands accrete due to their capacity to trap sediments and to incorporate dead leaves, branches, stems and roots into the soil, and they migrate driven by the preferred inundation conditions in terms of salinity and oxygen availability. Accretion and migration strongly interact, and they both depend on water flow and sediment distribution within the wetland, so wetlands under the same external flow and sediment forcing but with different configurations will respond differently to SLR. Analyses of wetland response to SLR that do not incorporate realistic consideration of flow and sediment distribution, like the bathtub approach, are likely to result in poor estimates of wetland resilience. Here, we investigate how accretion and migration processes affect wetland response to SLR using a computational framework that includes all relevant hydrodynamic and sediment transport mechanisms that affect vegetation and landscape dynamics, and it is efficient enough computationally to allow the simulation of long time periods. Our framework incorporates two vegetation species, mangrove and saltmarsh, and accounts for the effects of natural and manmade features like inner channels, embankments and flow constrictions due to culverts. We apply our model to simplified domains that represent four different settings found in coastal wetlands, including a case of a tidal flat free from obstructions or drainage features and three other cases incorporating an inner channel, an embankment with a culvert, and a combination of inner channel, embankment and culvert. We use conditions typical of south-eastern Australia in terms of vegetation, tidal range and sediment load, but we also analyse situations with 3 times the sediment load to assess the potential of biophysical feedbacks to produce increased accretion rates. We find that all wetland settings are unable to cope with SLR and disappear by the end of the century, even for the case of increased sediment load. Wetlands with good drainage that improves tidal flushing are more resilient than wetlands with obstacles that result in tidal attenuation and can delay wetland submergence by 20 years. Results from a bathtub model reveal systematic overprediction of wetland resilience to SLR: by the end of the century, half of the wetland survives with a typical sediment load, while the entire wetland survives with increased sediment load.

scholarly journals Accretion, retreat and transgression of coastal wetlands experiencing sea-level rise

2020 ◽  
Author(s):  
Angelo Breda ◽  
Patricia M. Saco ◽  
Steven G. Sandi ◽  
Neil Saintilan ◽  
Gerardo Riccardi ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Wetlands ◽  
Coastal Wetland ◽  
Sediment Load ◽  
Tidal Range ◽  
Sediment Distribution ◽  
And Migration ◽  
Wetland Evolution ◽  
Inner Channel

Abstract. The vulnerability of coastal wetlands to future sea-level rise (SLR) has been extensively studied in recent years, and models of coastal wetland evolution have been developed to assess and quantify the expected impacts. Coastal wetlands respond to SLR by vertical accretion and landward migration. Wetlands accrete due to their capacity to trap sediments and to incorporate dead leaves, branches stems and roots into the soil, and they migrate driven by the preferred inundation conditions in terms of salinity and oxygen availability. Accretion and migration strongly interact and they both depend on water flow and sediment distribution within the wetland, so wetlands under the same external flow and sediment forcing but with different configurations will respond differently to SLR. Analyses of wetland response to SLR that do not incorporate realistic consideration of flow and sediment distribution, like the bathtub approach, are likely to result in poor estimates of wetland resilience. Here, we investigate how accretion and migration processes affect wetland response to SLR using a computational framework that includes all relevant hydrodynamic and sediment transport mechanisms that affect vegetation and landscape dynamics, and it is efficient enough computationally to allow the simulation of long time periods. Our framework incorporates two vegetation species, mangrove and saltmarsh, and accounts for the effects of natural and manmade features like inner channels, embankments and flow constrictions due to culverts. We apply our model to simplified domains that represent four different settings found in coastal wetlands, including a case of a tidal flat free from obstructions or drainage features and three other cases incorporating an inner channel, an embankment with a culvert, and a combination of inner channel, embankment and culvert. We use conditions typical of SE Australia in terms of vegetation, tidal range and sediment load, but we also analyse situations with three times the sediment load to assess the potential of biophysical feedbacks to produce increased accretion rates. We find that all wetland settings are unable to cope with SLR and disappear by the end of the century, even for the case of increased sediment load. Wetlands with good drainage that improves tidal flushing are more resilient than wetlands with obstacles that result in tidal attenuation, and can delay wetland submergence by 20 years. Results from a bathtub model reveals systematic overprediction of wetland resilience to SLR: by the end of the century, half of the wetland survives with a typical sediment load, while the entire wetland survives with increased sediment load.

scholarly journals Success of coastal wetlands restoration is driven by sediment availability

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Zezheng Liu ◽  
Sergio Fagherazzi ◽  
Baoshan Cui
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Wetlands ◽  
Coastal Wetland ◽  
Meta Analysis ◽  
Regional Scale ◽  
Global Strategy ◽  
Sediment Supply ◽  
Tidal Range ◽  
Coastal Protection

AbstractShorelines and their ecosystems are endangered by sea-level rise. Nature-based coastal protection is becoming a global strategy to enhance coastal resilience through the cost-effective creation, restoration and sustainable use of coastal wetlands. However, the resilience to sea-level rise of coastal wetlands created under Nature-based Solution has been assessed largely on a regional scale. Here we assess, using a meta-analysis, the difference in accretion, elevation, and sediment deposition rates between natural and restored coastal wetlands across the world. Our results show that restored coastal wetlands can trap more sediment and that the effectiveness of these restoration projects is primarily driven by sediment availability, not by wetland elevation, tidal range, local rates of sea-level rise, and significant wave height. Our results suggest that Nature-based Solutions can mitigate coastal wetland vulnerability to sea-level rise, but are effective only in coastal locations where abundant sediment supply is available.

Coastal wetland substrate elevation is dynamically related to accommodation space and influenced by sea-level rise

2021 ◽  
Author(s):  
Kerrylee Rogers ◽  
Neil Saintilan
Keyword(s):  
Organic Matter ◽  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Wetlands ◽  
Coastal Wetland ◽  
Surface Elevation ◽  
Elevation Change ◽  
Accommodation Space ◽  
Sediment Volume ◽  
Surface Elevation Change

<p>The resilience of coastal wetlands in the fate of sea-level rise is proposed to be related to the combined influence of changes in substrate organic matter volume, mineral sediment volume, auto-compaction of accumulating material and deep subsidence; however, relatively few studies have measured all of these variables. In addition, there is ongoing debate about the suitability of this data for modelling the behaviour of coastal wetlands under anticipated sea-level rise projections as temporal discrepancies in the elevation response of coastal wetlands derived from observational and stratigraphic records exist. To resolve these issues, data derived from a range of techniques sensitive to changes occurring at annual, decadal and century timescales, is presented in the context of available accommodation space, that is, the space in which tidally-borne material can accumulate. Focussing on an embayment in Victoria, Australia, analyses confirm that at annual-decadal timescales, organic matter behaves like a sponge, compressing as the overburden of material accumulates, resulting in auto-compaction that modulates the degree of surface elevation change that occurs as tidally-borne material accumulates. These processes operate concurrently and are influenced by sediment availability, yet vary on the basis of available accommodation space. At longer timescales, the influence of auto-compaction diminishes as organic matter has undergone significant compression and decomposition, yet accumulated material remains proportional to available accommodation space. These analyses confirm that temporal discrepancies in rates of substrate elevation change can be resolved by accounting for the timescale over which processes operate and the influence of sea-level rise on available accommodation space. Accordingly, models should dynamically consider rates of surface elevation change relative to available accommodation space.</p>

Climate Change Impacts on a Mediterranean Coastal Wetland due to Sea Level Rise (L’Albufera de Valencia, Spain)

2021 ◽  
Author(s):  
Clara E Estrela Segrelles ◽  
Miguel Ángel Pérez Martín ◽  
Gabriel Gómez Martínez
Keyword(s):  
Climate Change ◽  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Wetlands ◽  
Coastal Wetland ◽  
Water Volume ◽  
Lake Ecosystem ◽  
Lake Levels ◽  
Short Term

<p>Sea level rise produced by climate change severely affects coastal ecosystems. The increase in the area below sea level facilitates the penetration of the marine wedge and causes an increase in soil salinity. Coastal wetlands are areas of great ecological importance due to the richness of flora and fauna that inhabit them. A change in salinity conditions could lead to a reduction or loss of habitat for the wetland biota. Based on RCP4.5 and RCP8.5 CMIP5 multimodel scenarios, in the Western Mediterranean coast, the sea level will rise 0.16 m in the short term (2026 - 2045) and 0.79 m in 2100. Also, high-end scenarios indicate that sea level will rise between 1.35 m and 1.92 m in the long term.</p><p>A sea level rise analysis has been developed in the coastal wetlands of Júcar River Basin District (JRBD). The results show that coastal wetlands are the mainly area affected in the JRBD, so the 90% of the area under the sea level are wetlands. L’Albufera de Valencia is the main wetland in this basin and, also the main wetland affected. It is an anthropized humid zone, regulated by users through gates to preserve the adequate water level for agricultural and environmental purposes such as rice cultivation around the lake and bird habitats conservation, especially in winter. The outcome of the study shows a significative increase in the area below the sea from 507 ha and 4.2 hm<sup>3</sup> of water volume at present to 3,244 ha that represents 42.6 hm<sup>3</sup> of water volume in the short term. In the long term, the area below the sea is 7,253 ha which means 118.4 hm<sup>3</sup> of water volume in the percentile 50 scenario and, in the worst extreme scenario, it is 13,896 ha that represents 289.7 hm<sup>3</sup> of water volume. This leads to a redefinition of the lake management levels as a climate change adaptation measure to prevent the lake salinization and severe impacts in the lake ecosystem. L’Albufera lake levels need to be increased in the next years to avoid the sea water penetration, related to the sea level rise. Thus, in the short term the lake levels must be increased around 0.16 m and, in the long term, L’Albufera levels must be increased around 0.8 m.</p>

Effects of increased salinity on tadpoles of two anurans from a Caribbean coastal wetland in relation to their natural abundance

2008 ◽  
Vol 29 (1) ◽  
pp. 7-18 ◽  
Author(s):  
Neftalí Rios-López
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Wetlands ◽  
Laboratory Experiments ◽  
Coastal Wetland ◽  
Salt Water ◽  
Larval Growth ◽  
Salt Water Intrusion ◽  
Climate Change Research ◽  
Water Intrusion

Abstract Many amphibians depend on wetland ecosystems for reproduction and survival, and coastal wetlands are not the exception. Recent advances on climate change research predict a reduction in land cover of coastal wetlands due to sea-level rise in response to global warming. Although this scenario will contribute to further amphibian population declines worldwide the impacts of sea-level rise and its related salt water intrusion on anuran assemblages in coastal wetlands remain largely unknown. I documented patterns of abundance of the native Caribbean white-lipped frog (Leptodactylus albilabris) and the introduced marine toad (Bufo marinus) along an inland-to-coastal salinity gradient in Puerto Rico. In addition, I investigated the effects of increasing salinity on larval growth and survival to metamorphosis in L. albilabris and B. marinus in laboratory experiments. In the field, relative abundance of adults of L. albilabris decreased with increasing salinity, while B. marinus showed the opposite pattern. Laboratory experiments with L. albilabris and B. marinus revealed that percentage of larvae surviving to metamorphosis in both species was greatly reduced in 22-25% seawater (8 ppt), which is within salinity levels found in their natural distribution. In this salinity level, the native L. albilabris showed ∼100% metamorphosis failure while the introduced B. marinus showed ∼60% metamorphosis failure. The reduction in metamorphosis was due to high mortality in L. albilabris and was accompanied with morphological abnormalities in B. marinus. Tadpoles of only L. albilabris reared for four weeks showed significant weight loss at 8 ppt, but showed no difference in length. These results suggest that anuran tadpoles may be living near their physiological limit for salinity in the studied wetland. Conservation implications are profound, however, as salt water intrusion and urban encroaching inland may result in anuran population replacement, from native species to introduced species in this wetland.

Can we avoid coastal squeeze through nature-based coastal adaptation?

2020 ◽  
Author(s):  
Mark Schuerch ◽  
Tom Spencer ◽  
Stijn Temmerman ◽  
Matthew Kirwan
Keyword(s):  
Ecosystem Services ◽  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Management ◽  
Coastal Wetlands ◽  
Coastal Wetland ◽  
Global Scale ◽  
Sediment Supply ◽  
Natural Habitats ◽  
Coastal Squeeze

<p>Intertidal coastal wetlands, including tidal marshes and mangrove forests, are at risk of disappearing under the influence of global sea level rise (SLR). Loss of their ecosystem services could significantly impact global carbon budgets, increase coastal erosion and flooding and lead to loss of fisheries, particularly along densely populated coastal zones such as large estuaries and deltas. Regional to global-scale projections suggest a reduction in present-day coastal wetland area by 20% to 90% in response to projected rates of future SLR. Recent studies have highlighted the importance of coastal squeeze, i.e. the inhibition of inland migration of tidal coastal wetlands due to the existence of anthropogenic infrastructure, in combination with wetland loss due to sea level rise, which is aggravated by a global decline in coastal sediment supply.</p><p>Nature-based adaptation, consisting of the reservation or creation of space for inland wetland expansion, is widely regarded as a promising strategy to counteract coastal squeeze and create/restore natural habitats through inland migration. Based on global and regional modelling outputs, this paper discusses how different scenarios of global population growth, expected declines in global sediment supply, delta subsidence and various coastal management strategies impact on global areas of intertidal coastal wetlands, and coastal squeeze in particular. For example, we estimate that until the year 2100 up to 280,000 km<sup>2</sup> of coastal wetlands may be lost due to coastal squeeze. If strategically implemented on a regional to global scale nature-based solutions to coastal management could increase the global total area of intertidal coastal wetlands by up to 60%.</p><p>However our current understanding of this process is very limited, partly due to the limited field evidence in sedimentary archives (e.g. during the early Holocene where SLR were high). We argue that this is related to the combined effects of wetland inland migration and wetland drowning during periods of high SLR rates, raising the question as to whether or not future coastal wetland will be able to provide ecosystem services comparable to those of natural systems.</p>

Physical-biological interactions limit the resilience of coastal wetlands to sea level rise

2021 ◽  
Author(s):  
Jose Rodriguez ◽  
Angelo Breda ◽  
Patricia Saco ◽  
Steven Sandi ◽  
Neil Saintilan ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Wetlands ◽  
Biological Interactions ◽  
Vegetation Types ◽  
Computational Framework ◽  
Sediment Loads ◽  
Long Time ◽  
And Migration ◽  
Wetland Evolution

<p>Predictions of the effects of sea-level rise over the next century on coastal wetlands vary widely due to uncertainties on environmental variables, but also due to simplifications on the simulation methodologies used. Here, we investigate how accretion and migration processes affect wetland response to sea level rise (SLR) using a computational framework that includes all relevant hydrodynamic, sediment transport and vegetation dynamics mechanisms that affect wetland evolution, and it is efficient enough computationally to allow the simulation of long time periods. We apply this framework to different settings typically found in coastal wetlands around the world, comprising different vegetation types, different sediment loads, obstructions to flow and drainage structures, both natural and man-made. We find that the vast majority of wetland settings analysed are unable to cope with high SLR rates and disappear before the end of the century. Our findings are consistent with paleo-records that indicate limits on the accretion capacity of coastal wetlands during periods of high SLR rates.</p>

scholarly journals Coastal wetlands can be saved from sea level rise by recreating past tidal regimes

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mahmood Sadat-Noori ◽  
Caleb Rankin ◽  
Duncan Rayner ◽  
Valentin Heimhuber ◽  
Troy Gaston ◽  
...  
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Coastal Wetlands ◽  
Environmental Crisis ◽  
Ground Vegetation ◽  
Proof Of Concept ◽  
Tidal Regime ◽  
Vegetation Sampling ◽  
Global Environmental ◽  
Intertidal Ecosystems

AbstractClimate change driven Sea Level Rise (SLR) is creating a major global environmental crisis in coastal ecosystems, however, limited practical solutions are provided to prevent or mitigate the impacts. Here, we propose a novel eco-engineering solution to protect highly valued vegetated intertidal ecosystems. The new ‘Tidal Replicate Method’ involves the creation of a synthetic tidal regime that mimics the desired hydroperiod for intertidal wetlands. This synthetic tidal regime can then be applied via automated tidal control systems, “SmartGates”, at suitable locations. As a proof of concept study, this method was applied at an intertidal wetland with the aim of restabilising saltmarsh vegetation at a location representative of SLR. Results from aerial drone surveys and on-ground vegetation sampling indicated that the Tidal Replicate Method effectively established saltmarsh onsite over a 3-year period of post-restoration, showing the method is able to protect endangered intertidal ecosystems from submersion. If applied globally, this method can protect high value coastal wetlands with similar environmental settings, including over 1,184,000 ha of Ramsar coastal wetlands. This equates to a saving of US$230 billion in ecosystem services per year. This solution can play an important role in the global effort to conserve coastal wetlands under accelerating SLR.

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